<?php
/**
 * @file
 * Example demonstrating a parent/child tabledrag form
 */

/**
 * Build the parent-child example form.
 *
 * @return
 *   A form array set for theming by theme_tabledrag_example_parent_form()
 *
 * @ingroup tabledrag_example
 */
function tabledrag_example_parent_form($form_state) {
  // Identify that the elements in 'example_items' are a collection, to
  // prevent Form API from flattening the array when submitted.
  $form['example_items']['#tree'] = TRUE;

  // Tabledrag will take care of updating the parent_id relationship on each
  // row of our table when we drag items around, but we need to build out the
  // initial tree structure ourselves.  This means ordering our items such
  // that children items come directly after their parent items, and all items
  // are sorted by weight relative to their siblings.
  // To keep this from cluttering the actual tabledrag code, we have moved
  // this to a dedicated function.

  // Fetch the example data from the database, ordered by parent/child/weight.
  $result = tabledrag_example_parent_get_data();

  // Iterate through each database result.
  foreach ($result as $item) {

    // Create a form entry for this item.
    //
    // Each entry will be an array using the the unique id for that item as
    // the array key, and an array of table row data as the value.
    $form['example_items'][$item->id] = array(

      // We'll use a form element of type '#markup' to display the item name.
      'name' => array(
        '#markup' => $item->name,
      ),

      // We'll use a form element of type '#textfield' to display the item
      // description, to demonstrate that form elements can be included in the
      // table. We limit the input to 255 characters, which is the limit we
      // set on the database field.
      'description' => array(
        '#type' => 'textfield',
        '#default_value' => $item->description,
        '#size' => 20,
        '#maxlength' => 255,
      ),

      // For parent/child relationships, we also need to add form items to
      // store the current item's unique id and parent item's unique id.
      //
      // We would normally use a hidden element for this, but for this example
      // we'll use a disabled textfield element called 'id' so that we can
      // display the current item's id in the table.
      //
      // Because tabledrag modifies the #value of this element, we use
      // '#default_value' instead of '#value' when defining a hidden element.
      // Also, because tabledrag modifies '#value', we cannot use a markup
      // element, which does not support the '#value' property. (Markup
      // elements use the '#markup' property instead.)
      'id' => array(
        // '#type' => 'hidden',
        // '#default_value' => $item->id,
        '#type' => 'textfield',
        '#size' => 3,
        '#default_value' => $item->id,
        '#disabled' => TRUE,
      ),

      // The same information holds true for the parent id field as for the
      // item id field, described above.
      'pid' => array(
        // '#type' => 'hidden',
        // '#default_value' => $item->pid,
        '#type' => 'textfield',
        '#size' => 3,
        '#default_value' => $item->pid,
      ),

      // The 'weight' field will be manipulated as we move the items around in
      // the table using the tabledrag activity.  We use the 'weight' element
      // defined in Drupal's Form API.
      'weight' => array(
        '#type' => 'weight',
        '#title' => t('Weight'),
        '#default_value' => $item->weight,
        '#delta' => 10,
        '#title_display' => 'invisible',
      ),

      // We'll use a hidden form element to pass the current 'depth' of each
      // item within our parent/child tree structure to the theme function.
      // This will be used to calculate the initial amount of indentation to
      // add before displaying any child item rows.
      'depth' => array(
        '#type' => 'hidden',
        '#value' => $item->depth,
      ),
    );
  }

  // Now we add our submit button, for submitting the form results.
  //
  // The 'actions' wrapper used here isn't strictly necessary for tabledrag,
  // but is included as a Form API recommended practice.
  $form['actions'] = array('#type' => 'actions');
  $form['actions']['submit'] = array('#type' => 'submit', '#value' => t('Save Changes'));
  return $form;
}

/**
 * Theme callback for the tabledrag_example_parent_form form.
 *
 * The theme callback will format the $form data structure into a table and
 * add our tabledrag functionality.  (Note that drupal_add_tabledrag should be
 * called from the theme layer, and not from a form declaration.  This helps
 * keep template files clean and readable, and prevents tabledrag.js from
 * being added twice accidently.
 *
 * @ingroup tabledrag_example
 */
function theme_tabledrag_example_parent_form($variables) {
  $form = $variables['form'];

  // Initialize the variable which will store our table rows.
  $rows = array();

  // Iterate over each element in our $form['example_items'] array.
  foreach (element_children($form['example_items']) as $id) {

    // Before we add our 'weight' column to the row, we need to give the
    // element a custom class so that it can be identified in the
    // drupal_add_tabledrag call.
    //
    // This could also have been done during the form declaration by adding
    // @code
    //   '#attributes' => array('class' => 'example-item-weight'),
    // @endcode
    // directly to the 'weight' element in tabledrag_example_simple_form().
    $form['example_items'][$id]['weight']['#attributes']['class'] = array('example-item-weight');

    // In the parent/child example, we must also set this same custom class on
    // our id and parent_id columns (which could also have been done within
    // the form declaration, as above).
    $form['example_items'][$id]['id']['#attributes']['class'] = array('example-item-id');
    $form['example_items'][$id]['pid']['#attributes']['class'] = array('example-item-pid');

    // To support the tabledrag behaviour, we need to assign each row of the
    // table a class attribute of 'draggable'. This will add the 'draggable'
    // class to the <tr> element for that row when the final table is
    // rendered.
    $class = array('draggable');

    // We can add the 'tabledrag-root' class to a row in order to indicate
    // that the row may not be nested under a parent row.  In our sample data
    // for this example, the description for the item with id '8' flags it as
    // a 'root' item which should not be nested.
    if ($id == '8') {
      $class[] = 'tabledrag-root';
    }

    // We can add the 'tabledrag-leaf' class to a row in order to indicate
    // that the row may not contain child rows.  In our sample data for this
    // example, the description for the item with id '9' flags it as a 'leaf'
    // item which can not contain child items.
    if ($id == '9') {
      $class[] = 'tabledrag-leaf';
    }

    // If this is a child element, we need to add some indentation to the row,
    // so that it appears nested under its parent.  Our $depth parameter was
    // calculated while building the tree in tabledrag_example_parent_get_data
    $indent = theme('indentation', array('size' => $form['example_items'][$id]['depth']['#value']));
    unset($form['example_items'][$id]['depth']);

    // We are now ready to add each element of our $form data to the $rows
    // array, so that they end up as individual table cells when rendered
    // in the final table.  We run each element through the drupal_render()
    // function to generate the final html markup for that element.
    $rows[] = array(
      'data' => array(
        // Add our 'name' column, being sure to include our indentation.
        $indent . drupal_render($form['example_items'][$id]['name']),
        // Add our 'description' column.
        drupal_render($form['example_items'][$id]['description']),
        // Add our 'weight' column.
        drupal_render($form['example_items'][$id]['weight']),
        // Add our hidden 'id' column.
        drupal_render($form['example_items'][$id]['id']),
        // Add our hidden 'parent id' column.
        drupal_render($form['example_items'][$id]['pid']),
      ),
      // To support the tabledrag behaviour, we need to assign each row of the
      // table a class attribute of 'draggable'. This will add the 'draggable'
      // class to the <tr> element for that row when the final table is
      // rendered.
      'class' => $class,
    );
  }

  // We now define the table header values.  Ensure that the 'header' count
  // matches the final column count for your table.
  //
  // Normally, we would hide the headers on our hidden columns, but we are
  // leaving them visible in this example.
  // $header = array(t('Name'), t('Description'), '', '', '');
  $header = array(t('Name'), t('Description'), t('Weight'), t('ID'), t('PID'));

  // We also need to pass the drupal_add_tabledrag() function an id which will
  // be used to identify the <table> element containing our tabledrag form.
  // Because an element's 'id' should be unique on a page, make sure the value
  // you select is NOT the same as the form ID used in your form declaration.
  $table_id = 'example-items-table';

  // We can render our tabledrag table for output.
  $output = theme('table', array(
    'header' => $header,
    'rows' => $rows,
    'attributes' => array('id' => $table_id),
  ));

  // And then render any remaining form elements (such as our submit button).
  $output .= drupal_render_children($form);

  // We now call the drupal_add_tabledrag() function in order to add the
  // tabledrag.js goodness onto our page.
  //
  // For our parent/child tree table, we need to pass it:
  // - the $table_id of our <table> element (example-items-table),
  // - the $action to be performed on our form items ('match'),
  // - a string describing where $action should be applied ('parent'),
  // - the $group value (pid column) class name ('example-item-pid'),
  // - the $subgroup value (pid column) class name ('example-item-pid'),
  // - the $source value (id column) class name ('example-item-id'),
  // - an optional $hidden flag identifying if the columns should be hidden,
  // - an optional $limit parameter to control the max parenting depth.
  drupal_add_tabledrag($table_id, 'match', 'parent', 'example-item-pid', 'example-item-pid', 'example-item-id', FALSE);

  // Because we also want to sort in addition to providing parenting, we call
  // the drupal_add_tabledrag function again, instructing it to update the
  // weight field as items at the same level are re-ordered.
  drupal_add_tabledrag($table_id, 'order', 'sibling', 'example-item-weight', NULL, NULL, FALSE);

  return $output;
}

/**
 * Submit callback for the tabledrag_example_parent_form form.
 *
 * Updates the 'weight' column for each element in our table, taking into
 * account that item's new order after the drag and drop actions have been
 * performed.
 *
 * @ingroup tabledrag_example
 */
function tabledrag_example_parent_form_submit($form, &$form_state) {
  // Because the form elements were keyed with the item ids from the database,
  // we can simply iterate through the submitted values.
  foreach ($form_state['values']['example_items'] as $id => $item) {
    db_query(
      "UPDATE {tabledrag_example} SET weight = :weight, pid = :pid WHERE id = :id",
      array(':weight' => $item['weight'], ':pid' => $item['pid'], ':id' => $id)
    );
  }
}

/**
 * Retrives the tree structure from database, and sorts by parent/child/weight.
 *
 * The sorting should result in children items immediately following their
 * parent items, with items at the same level of the hierarchy sorted by
 * weight.
 *
 * The approach used here may be considered too database-intensive.
 * Optimization of the approach is left as an exercise for the reader. :)
 *
 * @ingroup tabledrag_example
 */
function tabledrag_example_parent_get_data() {
  // Get all 'root node' items (items with no parents), sorted by weight.
  $rootnodes = db_query('SELECT id, name, description, weight, pid
                       FROM {tabledrag_example}
                       WHERE (pid = 0)
                       ORDER BY weight ASC');
  // Initialize a variable to store our ordered tree structure.
  $itemtree = array();
  // Depth will be incremented in our _get_tree() function for the first
  // parent item, so we start it at -1.
  $depth = -1;
  // Loop through the root nodes, and add their trees to the array.
  foreach ($rootnodes as $parent) {
    tabledrag_example_get_tree($parent, $itemtree, $depth);
  }
  return $itemtree;
}

/**
 * Recursively adds to the $itemtree array, ordered by parent/child/weight.
 *
 * @ingroup tabledrag_example
 */
function tabledrag_example_get_tree($parentitem, &$itemtree = array(), &$depth = 0) {
  // Increase our $depth value by one.
  $depth++;
  // Set the current tree 'depth' for this item, used to calculate indentation.
  $parentitem->depth = $depth;
  // Add the parent item to the tree.
  $itemtree[$parentitem->id] = $parentitem;
  // Retrieve each of the children belonging to this parent.
  $children = db_query('SELECT id, name, description, weight, pid
                      FROM {tabledrag_example}
                      WHERE (pid = :pid)
                      ORDER BY weight ASC',
                      array(':pid' => $parentitem->id));
  foreach ($children as $child) {
    // Make sure this child does not already exist in the tree, to avoid loops.
    if (!in_array($child->id, array_keys($itemtree))) {
      // Add this child's tree to the $itemtree array.
      tabledrag_example_get_tree($child, $itemtree, $depth);
    }
  }
  // Finished processing this tree branch.  Decrease our $depth value by one
  // to represent moving to the next branch.
  $depth--;
  // Return.
  return;
}
